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Sign of Advancing Society? An Organized War Effort

PLUNDER Ruins at Monte Alban in Oaxaca, Mexico. A wave of new research holds that early states arose from warring chiefdoms as populations grew.Credit
Beth Greenfield for The New York Times

Some archaeologists have painted primitive societies as relatively peaceful, implying that war is a reprehensible modern deviation. Others have seen war as the midwife of the first states that arose as human population increased and more complex social structures emerged to coordinate activities.

A wave of new research is supporting this second view. Charles Stanish and Abigail Levine, archaeologists at the University of California, Los Angeles, have traced the rise of the pristine states that preceded the Inca empire. The first villages in the region were formed some 3,500 years ago. Over the next 1,000 years, some developed into larger regional centers, spaced about 12 to 15 miles apart. Then, starting around 500 B.C., signs of warfare emerged in the form of trophy heads and depictions of warriors, the two archaeologists report in last week’s Proceedings of the National Academy of Sciences.

One of the regional centers, Taraco, was destroyed in the first century A.D., probably by forces from Pukara, the other principal regional center of the area. Pukara enjoyed its status as a pristine state until about 500, when it was absorbed by Tiwanaku, the principal state on the other side of the Lake Titicaca basin.

A similar process of an early state’s arising from warring chiefdoms has been described in the Oaxaca Valley of Mexico by Kent V. Flannery and Joyce Marcus, archaeologists at the University of Michigan. By 4,500 years ago, there were some 80 villages in the valley. As population increased, a period of intense warfare lasted from 2,450 to 2,000 years ago, culminating in the victory of one town over all the others in the valley and the formation of the Zapotec state.

With the same process now documented in both North and South America, “we are coming closer to having a model for pristine state formation that may have worldwide significance,” Dr. Marcus said. “It also shows that our species, when thrust into almost identical circumstances, behaves in almost identical ways.”

Dr. Stanish believes that warfare was the midwife of the first states that arose in many regions of the world, including Mesopotamia and China as well as the Americas.

The first states, in his view, were not passive affairs driven by forces beyond human control, like climate and geography, as some historians have supposed. Rather, they were shaped by human choice as people sought new forms of cooperation and new institutions for the more complex societies that were developing. Trade was one of these cooperative institutions for consolidating larger-scale groups; warfare was the other.

Warfare may not usually be thought of as a form of cooperation, but organized hostilities between chiefdoms require that within each chiefdom people subordinate their individual self-interest to that of the group.

“Warfare is ultimately not a denial of the human capacity for social cooperation, but merely the most destructive expression of it,” the anthropologist Lawrence H. Keeley writes in his book “War Before Civilization” (Oxford, 1996).

Compared with other species, humans are highly cooperative and altruistic, at least toward members of their own group. Evolutionary biologists have been hard pressed to account for this self-sacrificing behavior, given that an altruist who works for the benefit of others will have less time for his family’s interests and leave fewer surviving children. Genes for altruistic behavior should therefore disappear.

Darwin’s solution to this riddle was that groups of altruists would prevail over less cohesive groups. This implies that natural selection can operate on groups, not just individuals, a thesis that many biologists reject.

But group-level selection is more likely to operate the fiercer the competition is between groups. Samuel Bowles, an economist at the Santa Fe Institute, believes warfare between early human groups was intense, and explains the very slow growth of population prior to 20,000 years ago.

Warfare “may have contributed to the spread of human altruism,” he and his colleague Herbert Gintis write in their new book, “A Cooperative Species”(Princeton, 2011). “We initially recoiled at this unpleasant and surprising conclusion. But the simulations and the data on prehistoric warfare tell a convincing story.”

Archaeology lends some support to the idea. “Groups that successfully organize themselves to raid others will acquire external resources and, in the long run, will be at a selective advantage against groups that are less well organized,” Dr. Stanish and Dr. Levine write of their findings in the Central Andes.

“Both war and trade are sources of outside wealth,” Dr. Stanish said in an interview. The leaders of early states had to keep people working. They relied on religious rituals to organize the labor force and material inducements from war and trade to satisfy the elite.

As the population in a region grew larger and richer, regional chiefdoms would form and start raiding one another for plunder. “Once this kicks in, it sets up a dynamic in which it’s hard to be peaceful,” Dr. Stanish said. “You either organize on a regional level or get killed or absorbed.”

Of the regional chiefdoms that start a war for dominance, all but one will perish before the pristine state is formed. So why not form nonaggression pacts rather than take such a gamble?

Dr. Marcus suggests two reasons. One is that human social skills evolved in the small hunter-gatherer groups in which everyone lived until 15,000 years ago. “When humans try to run larger and more complex societies, with hereditary inequality, they are pushing their sociopolitical skills to the utmost,” Dr. Marcus said.

Another reason is that elites who run chiefly societies “are very aggressive and competitive — they assassinate rivals even when they are siblings or half-siblings,” Dr. Marcus said. “Competitive interaction is one of the most powerful driving forces in evolution, whether biological or social.”

A version of this article appears in print on August 2, 2011, on page D4 of the New York edition with the headline: Sign of Advancing Society? An Organized War Effort. Order Reprints|Today's Paper|Subscribe